Arsenite binding

Arsenite (binds to ArsR protein and removes it from operator site)... 

Figure 5 Structure of the molybdenum center in xanthine oxidase. The sulfido ligand to molybdenum is the site at which arsenite binds in xanthine oxidase. This group is absent in arsenite oxidoreductase.

In REACT, we prepare the calculation by disenabling the redox couple between trivalent and pentavalent arsenic (arsenite and arsenate, respectively). As well, we disenable the couples for ferric iron and cupric copper, since we will not consider either ferrous or cupric species. We load dataset FeOH+.dat , which contains the reactions from the Dzombak and Morel (1990) surface complexation model, including those for which binding constants have only been estimated. The procedure is... 

Wijeweera, J. B. et al., Sodium arsenite enhances AP-1 and NFkappaB DNA binding and induces stress protein expression in precision-cut rat lung slices, Toxicol. Sci., 61, 283, 2001. 

The mobilization of arsenic from the tailings material seems to be a slow and continuos process attributed to reduction of iron phases. The seepage water of the middle source contains arsenite as well as arsenate in high concentrations and seems to be the only water source in contact with the tailings material. The concentrations of arsenic downstream are still high and the immobilization process by precipitation of iron hydroxide and coprecipitation or sorption of arsenic is incomplete. A reason for this may be the slow kinetics of the oxidation process and the transport of fine grained hydroxide particles. These particles are mobile and can bind the arsenic (mainly as arsenate) too. 

Some compounds of this type may have a high affinity for proteins that is not due to their binding to two thiol groups (35). In particular, arsenite also reacts with the molybdenum-pterin cofactor of many enzymes (35a-d). This usually inhibits the enzyme, but in particular cases (35e) the arsenite may be oxidized indeed the enzyme arsenite oxidase contains such a center (35f). 

In E. coli arsenate is reduced to arsenite by a glutare-doxin-andNADH-dependentsystem s Thearsenite as well as antimonite and tellurite are pumped out by an ATP-dependent transporter. The genes for reductase, periplasmic-binding protein, and transporter components are encoded in a conjugative plas-midA1 A quite similar system functions in yeast.)... 

The presence of suitable reductants (or oxidants) is essential. These effects are examined here for As(III)/As(V) and Cr(III)/ Cr(VI). The redox states of trace elements affect their solubility (e.g., Cr(III)/Cr(VI)) and their affinity for binding to solid phases (e.g., arsenite and arsenate). Biological effects (e.g., uptake and toxicity) are also dependent on the redox state. 

Buschmann, J., Kappeler, A., Lindauer, U. et al. (2006) Arsenite and arsenate binding to dissolved humic acids influence of pH, type of humic acid, and aluminum. Environmental Science and Technology, 40(19), 6015-20. 

Vahter, M., Marafante, E., Lindgren, A. and Dencker, L. (1982) Tissue distribution and subcellular binding of arsenic in marmoset monkeys after injection of 74As-arsenite. Archives of Toxicology, 51(1), 65-77. 

Shumilla JA, Wetterhahn KE, and Barchowsky A. 1998. Inhibition of NF-kB binding to DNA by chromium, cadmium, mercury, zinc, and arsenite in vitro Evidence of a thiol mechanism. Arch Biochem Biophys 349(2) 356-362. 

Trivalent inorganic arsenicals, such as arsenite, readily react with sulfhydryl groups, such as GSH and cysteine (Scott et al, 1993 Delnomdedieu et al, 1994). The complex between arsenic and the vicinal sulfhydryl group is particularly strong. Arsenite inhibits pyruvate dehydrogenase (PDH) activity (Hu et al, 1998), perhaps by binding to the... 

In some of the organisms, the ars operon arsRDABC) consists of five genes with two additional components arsA and arsD which code for two additional proteins. arsD exhibits weak As(lll)-responsive transcriptional repressor activity (Lin et al, 2007 Chen and Rosen, 1997). The arsA codes for intracellular ATPase proteins which bind as a dimer to the arsenic membrane efflux pump coded by arsB to provide the higher levels of As(III) resistance (Rosen, 2002b). The arsenite membrane efflux pump is unique in that it can function either chemiosmotically (alone) or as an ATPase (dimer complexes). 

Trivalent arsenic is less abundant in nature, but considerably more toxic. Detoxification of arsenite results in the same methylated species as those arising from arsenate. However, because trivalent arsenic binds tightly to thiol-containing molecules in tissues, it is much less easily detoxified and excreted. 

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